Georgia's supply of pentobarbital expired in March, and has not secured a supply in sufficient quantity to put Hill to death. Photograph: Linda Nylind for the Guardian

The state of Georgia is scrambling to obtain a new supply of the sedative pentobarbital for use in lethal injections ahead of the scheduled execution of Warren Hill on Monday night.

The Georgia corrections department confirmed that, with just days to go before Hill's death sentence is due to be carried out, it has not yet secured a batch of the medical drug in sufficient quantity to kill him. The department's existing stock of pentobarbital expired in March, and the Guardian understands that the state has turned to an unidentified compounding pharmacy in another state to try and skirt around international controls.

The ungainly spectacle of a US state desperately seeking a supply of pharmaceutical in order to kill a man provides a snapshot of the dire condition of the death penalty in many of the 32 states that still practice it. An international boycott of trade in medicines to corrections departments for use in executions, led by the European Commission, has reduced stocks to such a low level that many states are struggling to carry out any executions at all.

In an attempt to circumvent international and national scrutiny, the Georgia state assembly passed a law in March that in effect permitted the corrections department to act in secret in seeking to acquire execution drugs. The provision classifies the identity of any person or company providing drugs for use in lethal injections as a "state secret", thereby negating any public right to the information.

It also allows the corrections department to keep secret the identity of doctors who collaborate with executions by administering lethal injections in contravention of their ethical code.

Warren Hill, 53, has been granted a stay of execution from the federal appeals court for the 11th circuit. Photograph: Ho/AFP/Getty Images

Brian Kammer, the defence attorney for Hill, pictured, said he was "searching for words to express my disgust at this process. The secrecy in this context to me invokes images of lynchings by hooded men – it's very emblematic of an earlier time in the south."

Kammer added that in his view this was a "shameful, reprehensible, cowardly way of killing people."

Georgia corrections department said that it was confident that it would obtain sufficient drugs in time for Monday's 7pm execution of Hill. It said that the current protocol would be followed of injecting the prisoner with 5g of the single drug pentobarbital.

Like other death penalty states, Georgia was forced to drop its three-drug lethal injection protocol when the US manufacturer Hospira ceased making the anaesthetic sodium thiopental after the company came under pressure from authorities in Italy. The state moved to the single drug pentobarbital, but that also was hit by the boycott when a major manufacturer of the drug, the Danish firm Lundbeck, strictly restricted sales to prohibit its product ending up in the death chamber.

In extremis, Georgia even turned to an unlicensed company called Dream Pharma that operated out of a driving school in Acton, west London.

As a result of Georgia's new secrecy law, that hides the identity of the sources of the drugs, it is not known where the corrections department is attempting to get hold of pentobarbital before Monday. But the fine print of the law contains clues: it classes as a state secret the identity of "any person or entity that manufactures, supplies, compounds or prescribes the drugs".

The use of compounding pharmacies to create small batches of drug to order has been highly controversial in the US. The Food and Drug Administration has struggled to bring the outlets under rigorous supervision.

Other states including Arkansas, South Dakota and Tennessee have also introduced secrecy provisions designed to foil the boycott by keeping the identities of suppliers hidden. But lawyers and human rights groups have protested against the creeping secrecy in something as fundamental as the judicial taking of life.

Maya Foa, a death penalty drugs expert with Reprieve, said that lack of scrutiny meant it would be more difficult to ensure that the execution did not stray into torture or cruel and unusual punishment. "I would question what Georgia has to hide," she said.

Sara Totonchi of the Atlanta-based Southern Center for Human Rights said that by shrouding the supply route in secrecy "they are cutting off from the public an act that is desperately needed – oversight."

In October 2012 an outbreak of fungal meningitis in the US was traced back to a compounding center in Massachusetts.

Hill would be the first death row inmate in Georgia to be executed after the introduction of the new secrecy law. His case is singularly controversial as he has been found by multiple medical experts to be intellectually disabled – a developmental condition still known in US jurisprudence as "mental retardation" that renders him constitutionally barred from execution.